Character-based languages (e.g., Chinese, Japanese, Korean, etc.) have thousands of characters, making it difficult for users to enter the intended characters or words into computers or electronic devices. Language specific keyboards do not exist for the simple fact that it is practically impossible to build a keyboard to support separate keys for so many different characters.
Accordingly, users typically employ a small character-set keyboard (e.g., an English QWERTY keyboard) to enter phonetic text and then word processing software converts the phonetic text to the appropriate language text of a character-based language. “Phonetic text” represents the sounds made when speaking a given language, whereas the “language text” represents the actual written characters as they appear in the text. In the Chinese language, for example, Pinyin is an example of phonetic text and Hanzi is an example of the language text. Typically, the set of characters needed to express the phonetic text is much smaller than the character set used to express the language text.
While the entry of phonetic text is difficult on small character-set keyboards, the problem is exacerbated when moving to mobile devices that are commonly equipped with input mechanisms with fewer keys. For instance, a cellular phone commonly has only eight keys to represent all 26 English letters. As a result, attempting to enter phonetic text, such as Chinese Pinyin, into a cellular phone using only a few keys can be very confusing. From a language processing perspective, the problem is twofold. First, an input system must recognize with confidence one or more possible syllables of approximately 406 syllables from a string of numbers entered using eight keys 2-9 on a common 10-key keypad. Inputting, for example, the single letter “z” might require a user to type “9999” in some products. Entering two or three characters without error in an effort to enter an intended syllable can therefore pose problems. It is noted that this problem also exists for input of English characters on mobile phone.
Second, the system must map the recognized syllable candidates to one or more than 6,000 common Chinese characters. Syllable to character conversion is a very difficult process, even for large-scale computers with substantial processing capabilities. The problem is made more difficult in the context of a limited-resource computing environment, such as a mobile phone.
Given these problems, there is a continuing need for new methods that allow a user to enter phonetic characters (e.g., Pinyin) into a mobile device with as few keys as possible, and then automatically choose the most likely language character (e.g., Hanzi character) that the user intended.